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Small 2-way speakers with linear on-axis and power response characteristics (Scan Speak and SB Acoustics drivers). H&V off-axis measurements included
- Thread starter XMechanik
- Start date
Roland68
Master Contributor
Everything about this is as bad and wrong as it could possibly be.
Anyone who relies on AI's predictions in the audio field is doomed. This is proven time and again.
The crossover for the subwoofer is unusable.
The inductor for the low-pass filter must be in the signal path to the woofer, not in parallel.
The capacitor for the low-pass filter must be in parallel with the woofer, not in series.
A coil specification for such a coil without a resistance value is useless.
An inductor in the signal path without considering the saturation current is unusable.
The passive radiator is incorrectly dimensioned.
The subwoofer driver's specifications indicate a significant impedance mismatch with the Mechano23 when using a passive crossover (too quiet).
The lack of a high-pass filter for the Mechano23 reduces its sound quality to that of a cheap party speaker. Furthermore, it could be damaged at high volumes because the low frequencies are not filtered.
A subwoofer enclosure made of 18mm plywood? You can do it, but you can also just forget about it.
High-pass and low-pass filters are necessary for a halfway decent result.
With the expected cutoff frequency of 60-150 Hz, high-quality components are already so expensive and inflexible that an active crossover with an additional amplifier is definitely the better choice. A stereo amplifier with 2 x 100-150 watts and an active crossover with 4 output channels can be found for as little as €200 and makes much more sense.
Nevermind the schematic, wtf is this graph even?
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It's a plot of FPecnsse vs. Frequency. Problem with that??
Roland68
Master Contributor
The correct dimensions are probably 32 x 58 mm.This one is listed as 7 x 18mm but I'm skeptical if that is true :
Jantzen Audio 27uF 400V Cross Cap Crossover Capacitor
Jantzen Audio 27uF 400V Cross Cap Crossover CapacitorProduct FeaturesDimensions: (Ø 7mm - L: 18mm)The Cross Cap is offering a high-level of performance and quality at a very reasonable price point. A great multipurpose entry-level audiophile capacitor. A single foil (standard type MKP/PP foil)...www.parts-express.com
and its more expensive @~ $16 each.
You could take a look at industrial-grade MKP capacitors from Kemet and Epcos/TDK. 27uF 800V capacitors start at around €5, and 1000-1100V capacitors start at around €10.
Significantly better electrical properties and cheaper. I've been using them for over 20 years.
sebastian k
New Member
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- Mar 14, 2025
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Thanks a lot for your clarifications. They helped a lot. And sorry, I did not reply sooner - I was quite busy in December...
Internal stuffing seems to make the difference here whereas box volume doesn't seem to make too big of a difference. Another thing that might have helped is that I improved my temporary enclosure. I sealed up some leaks and added regidity - basically it's the front baffle and a bunch of wood clamps at this time ;-)
Anyways - results are not perfect, but probably close enough and definitely better than my preveous attempt. Red is the original Mechano 23, blue is the sealed version.
I do have the original baffle wall and an internal depth of 11.5 cm with 19mm MDF. So the volume is just under 4 l. The effecive internal volume is smaller of course because of the drivers and the crossover.
Stuffing is one layer of this visaton polyester wool on the side walls and the top and bottom walls.
Additional stuffing behind the tweeter as you proposed did make things worse.
glampersand
New Member
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- Oct 12, 2020
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Hey Y'all, it's been something like 20 years since I last built a set of speakers and I'm thinking of doing a set of these to be my new main set. (My last build was a set of Selah Audio RCR3, which I know the sealed version didn't measure well here but I've loved my ported set — I'd still be using them they fit in my space better!) Planning them to take the place of an old set of AV123 ELT525 in a roughly 25' x 14' living room, paired with a Wiim amp and SVS PB2000 sub. I know they're a bit small for that kinda space but we don't listen at particularly high levels and the AV123 set are also just 5" woofer bookshelfs that have been fine output-wise when combined with the sub crossed round 80hz.
A quick question before I put in the orders. Right now I've got the crossover parts from the OP in a couple different shopping carts, and I'd really like to try a rear mounted passive radiator, mainly because I've not built with one before and it seems fun to try. Through this 40 page thread and the review thread there's a bit of talk about alternate crossover options — is there anything I should definitely look at doing different than in the OP? I've got all the right values tracked down so that's not a concern, but I don't know enough about crossover design to have a sense of what's smarter folks just noodling on on things that might add a hair of improvement vs obvious upgrades.
A quick question before I put in the orders. Right now I've got the crossover parts from the OP in a couple different shopping carts, and I'd really like to try a rear mounted passive radiator, mainly because I've not built with one before and it seems fun to try. Through this 40 page thread and the review thread there's a bit of talk about alternate crossover options — is there anything I should definitely look at doing different than in the OP? I've got all the right values tracked down so that's not a concern, but I don't know enough about crossover design to have a sense of what's smarter folks just noodling on on things that might add a hair of improvement vs obvious upgrades.
You don't need a passive radiator if you plan on using them with subs. The PR's that would work aren't exactly cheap either.
glampersand
New Member
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Planning to keep them for a long time and in 5-10 years when the kids are a bit less of a menace I’ll probably rearrange and use these on their own somewhere. I’d been looking at the SB 5x8 which is more expensive than a tube but if it’s another 20 years before I build another set may as well live a little.
ChillHippo
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Long time lurker, first time poster. I finished a test unit the other day and finally got to measuring, design mirrors the reference with one primary change to the enclosure shape and port location. It is mounted to the wall using a french cleat with a rear 1" cavity to give room for the cleat and in-wall cable, making it a fantastic Theater side and rear designs.
Used the port and PCB from wineds (thank you!). 1/2" mdf, doubled for the front, face of it has the same dimensions as the reference post then widens out to net ~8L, port on the bottom roughly center.
Sharing as someone might be interested in the general design of it and results.
Seating position in non-treated room, the drop at 95, 285, and 365hz seem room related as they change with different speaker locations.
Off to build the next 3 and make this one look pretty.
Used the port and PCB from wineds (thank you!). 1/2" mdf, doubled for the front, face of it has the same dimensions as the reference post then widens out to net ~8L, port on the bottom roughly center.
Sharing as someone might be interested in the general design of it and results.
Seating position in non-treated room, the drop at 95, 285, and 365hz seem room related as they change with different speaker locations.
Off to build the next 3 and make this one look pretty.
Attachments
Do you have pics of your arrangement? Would love to take a look at them.
Bit late but that's the only picture i have. I used the 3D printed plate for the crossover. But it is quite wobbly and soft.
Edit: this is zoomed because the images seems to get compressed:
Roland68
Master Contributor
The fact that the plate is soft is partly due to its structure.
For maximum hardness, PC or PC GF would be suitable materials.
Closed surfaces on both sides with 15-25% infill, adding only the necessary holes. Alternatively, a grid of holes with 7-10mm spacing can be used.
For even greater stability, the edge can be reinforced with a profile, and a 3D structure can be used on the top and/or bottom, similar to what is used in aluminum or magnesium die casting. This can also be designed as a part divider or snap-in fastener.
For anyone planning to print something like this: CF filaments are unsuitable due to their potential conductivity, unless adequate insulation is used.
I really like that idea of 3D printing the front and using wood elsewhere. I'm the one who did the full 3D printed cases, but was just suggesting to someone that this hybrid approach was brilliant.
FWIW, I'd done lots of testing on materials and infill vs. resonance of panels. That's what led me to PET-G.
FWIW, I'd done lots of testing on materials and infill vs. resonance of panels. That's what led me to PET-G.
- Thread Starter
- #794
I think 3D printing the front panel flushes is a great idea, and I definitely have to try it. It avoids potentially risky, noise and dust generating operations with a router machine. Just a technical question: if the "PE-G" in the filament name stands for polyethylene, is there a good method for firmly and permanently gluing the print on plywood? Polyethylene makes me think of gluing problems, and from what I can see, the @klapper 3D print is attached with screws. Is this the only effective method?
Roland68
Master Contributor
The material he's referring to is PETG. PETG is difficult to glue.
I would always recommend PC for this kind of thing; it's harder and much easier and more durable to glue. Even greater hardness can be achieved with glass or carbon fiber.
It bonds very well with all kinds of superglue, epoxy resins, solvent-based welding adhesives (e.g., acetone or methylene chloride based), RTV-1 silicone adhesive (e.g., ELASTOSIL E43 RTV-1), and various acrylic/polycarbonate adhesives.
To achieve a good bonding surface, it's best to print on cheap PEI (non-"smooth") build plates from AliExpress without glue or adhesion promoters. These build plates have a sandpaper-like surface and create a perfectly rough bonding surface. Don't use the good plates from Bambu Lab; they're too smooth.
IIRC, I used JB Weld for plastic during assembly of the parts. Here, having some screws either go from the face into your plywood or the reverse would also seem to solve the problem. A little bead of caulk and 4 screws should hold things together quite nicely and seal it up as well.
I used PLA because i still had some in a color i liked.
Since there is a 9mm wood layer i assume the material will not make huge differences.
I use screws for many reasons:
1) it's replaceable 1.2) i might wan't to change to different colors/ designs 1.3) If the PLA gets damaged i can replace it easier 1.4) i was not sure how PLA will behave after years (Dehydration, cracks, color changes, bending) 2) screws can look cool
I put a thin layer sealing dough (Egoform) between the wood and Front and screwed it in.
For printing i suggest the front to be placed on the build plate. And don't do my mistake:
First, print a small test print to check which radius produces a good result: preferably without support material, as this may be visible later. Perhaps an angled edge would also be easier to print here.
I've been wondering for a while now what it would look like if the horn for the tweeter were integrated directly into the front. But I don't know if that works with this tweeter model nor how to copy the EXACT horn shape and size.
Since there is a 9mm wood layer i assume the material will not make huge differences.
I use screws for many reasons:
1) it's replaceable 1.2) i might wan't to change to different colors/ designs 1.3) If the PLA gets damaged i can replace it easier 1.4) i was not sure how PLA will behave after years (Dehydration, cracks, color changes, bending) 2) screws can look cool
I put a thin layer sealing dough (Egoform) between the wood and Front and screwed it in.
For printing i suggest the front to be placed on the build plate. And don't do my mistake:
First, print a small test print to check which radius produces a good result: preferably without support material, as this may be visible later. Perhaps an angled edge would also be easier to print here.
I've been wondering for a while now what it would look like if the horn for the tweeter were integrated directly into the front. But I don't know if that works with this tweeter model nor how to copy the EXACT horn shape and size.
Aaronb1138
Member
This post on the port tuning is almost 2 years old, but regarding port air velocity and linearity, another DIY solution which would also make testing different tunings could be using the Harman / Stouhal port as designed and optimized by augerpro and stv at diyaudio.com and 3D printing the different tunings and testing. I am using one of these with the CAD file reworked to fit the opening already in the design in a Seas "Loki" coaxial bookshelf kit speaker at the moment. They are also actively working on port resonance in the thread below but have not quite landed on a satisfactory universal solution.
Main thread: https://www.diyaudio.com/community/...sonance-absorbers-and-port-geometries.388264/
Port parameters optimization spreadsheet: https://www.diyaudio.com/community/threads/investigating-port-resonance-absorbers-and-port-geometries.388264/page-54#post-8102675
FreeCAD file: https://www.diyaudio.com/community/...rbers-and-port-geometries.388264/post-7705828
For ports and any kind of waveguide, I am pretty much on the side of using SLA / resin 3D printing as the surface finish is close to acoustically smooth out of the printer compared to FDM. I am getting into FDM printing recently with a Snapmaker U1 setup this weekend and doing tests of using a PLA + TPU sandwich as constrained layer dampening for full cabinets with positive results so far. FDM print smoothness has improved, but I would still stick with resin for ports and waveguides versus STV's print split and significant filler and sanding approach.
wineds
Active Member
@Aaronb1138 Thanks for posting. So a more optimum port for Mechano23 might look something like this :
Aaronb1138
Member
You might take a look at the STR fields under "Result" on the second tab for the Strouhal number. For that configuration, the Strouhal number ends up around 0.705. From their research in that thread, Strouhal numbers =1 or >1 are preferable for little to no turbulence. If you bump the tuning frequency to 51-53 Hz as @Maiky76 suggested, you end up with a Strouhal number of 1.021-1.158.
Also note that the 45 Hz tuning is pretty close to the un-flared standard tube port in the original design - 145x35mm vs 147x34mm (Dmin), though the suggested port is continually expanding in each direction / tapering to center to reduce turbulence. The 51 Hz tuning goes a bit shorter and wider -- 130x35mm (Dmin).
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